In a flooring work, for example, when a work for driving a nail into furring of floor material is conducted, minute wooden trash sometimes falls on the furring. In case where finishing material is overlaid on the furring in this state to drive another nail, the finishing material may float because of existence of the wooden trash on the furring, and the work must be started again from the beginning. In order to prevent such inconvenience, it has been heretofore accustomed to set the finishing material, after a surface of the furring has been cleaned away with an air duster, and then, conduct the work for driving the nail. However, because the air duster is separately provided from a nailing machine, it has been necessary to frequently exchange the nailing machine with the air duster, which has been extremely annoying.
Under the circumstances, in order to solve the above described inconvenience, a nailing machine provided with an air duster in itself has been known (Reference should be made to Patent Documents 1, 2 and 3). According to such structure, there is no need of exchanging the nailing machine with the air duster at every time.    Patent Document 1: Japanese Patent No. 3385875    Patent Document 2: Japanese Patent Publication No. JP-A-2004-1135    Patent Document 3: Japanese Patent Publication No. JP-A-2004-1136
However, the nailing machine provided with the air duster as described above has the following drawbacks.
(1) Because the compressed air for the air duster is taken out from the same section as an air chamber (an accumulator), oil which has been supplied to a body of the nailing machine is circulated to the air duster together with soil or the like of a hammering mechanism, and discharged. The oil which has been soiled and discharged adheres to the finishing material, and a problem of damaging an object material may occur.(2) Because the compressed air is directly blown out from the air chamber, a blowing direction of the compressed air is different from a direction of ejecting a fastener. Therefore, when a worker uses the air duster, a direction of the pneumatic tool must be changed, which incurs bad workability. Moreover, in case where an object substance (wooden trash, for example) is small, it is difficult to target it.(3) When the worker drives a nail into a deep corner at a lower side, he changes his hand to grip the pneumatic tool for convenience, and operates a trigger lever with his little finger, in many cases. On this occasion, the worker sometimes unconsciously presses an operating button of the air duster with his hand. In this case, because the compressed air for the air duster is taken out from the same section as the air chamber, an air pressure inside the air chamber may be lowered, and dust in vicinity of a working site may be scattered, which results in bad workability.(4) A position where the worker grasps a grip of the pneumatic tool to put a finger on the trigger lever is slightly offset from a position where the worker puts a finger on the operating button. Therefore, when he uses the air duster, he must grasp the grip again to re-start the work, which incurs bad operability.(5) The pneumatic tool is connected to a compressed air supply source by way of an air hose. Therefore, in case where the pneumatic tool placed on the floor is at a remote position, the pneumatic tool is sometimes drawn near, by pulling the air hose. On this occasion, the pneumatic tool is likely to be caught by a pillar or the like, and the operating button is pressed by the pillar or the like to actuate the air duster, in some cases.(6) In case where high-pressure air is used, because the ejected air has a high pressure, wooden trash or the like is often blown off more than required. For solving this problem, there has been such a nailing machine that a pressure reducing valve is provided in an air pipeline communicated with a nozzle (Reference should be made to Patent Document 3). However, this nailing machine is heavy, because of increase of components in number, which has been a factor of high cost.